1. Field of the Invention
The present invention relates to a motorcycle including a belt type continuously variable transmission having a resin block belt.
2. Description of Related Art
A motorcycle including a belt type continuously variable transmission is known in the art (for example, see JP-A-2002-147582). A belt type continuously variable transmission includes a V-belt wound around primary and secondary sheaves. A driving force of a crankshaft of an engine is transmitted in the order of the primary sheave, the V-belt, and the secondary sheave. The driving force is transmitted to a driving wheel after a speed is changed. The primary sheave, V-belt, and secondary sheave are housed in a belt chamber formed inside the transmission casing.
In JP-A-2002-147582, a resin block belt is used to improve durability of the V-belt and prevent heat generation due to deformation. The resin block belt includes a large number of resin blocks coupled together by coupling members. However, because the resin blocks are separated from each other, they tend to collide with each other while the V-belt is running. Therefore, a resin block belt tends to cause more noise than a rubber belt.
In consideration of this problem, JP-A-2002-147582 suggests disposing a sound absorption material on an inner surface of the transmission casing accommodating the resin block belt to prevent noise. However, the V-belt runs at a high speed, and the primary and secondary sheaves rotate at high speeds. Therefore, the sound absorption material must not contact the V-belt and sheaves and must be disposed a certain distance away from the V-belt and sheaves. Therefore, if the sound absorption material is disposed on the inner surface of the transmission casing as in JP-A-2002-147582, a space for the sound absorption material must be provided inside the transmission casing. However, the belt chamber volume is increased if extra space for the sound absorption material is provided. Therefore, the motorcycle of JP-A-2002-147582 has a problem that the belt type continuously variable transmission is increased in size.
A sound absorption material normally also has a thermal insulation function. Therefore, a temperature inside the belt chamber is apt to rise when sound absorption material is provided on the inner surface of the transmission casing. Thus, there is a problem that the durability of the resin block belt is decreased due to a temperature increase in the belt chamber.